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Thread: M35A3 tires all flat on one side of the truck?

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    Sergeant HDN's Avatar
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    Default M35A3 tires all flat on one side of the truck?

    I'm looking at purchasing an M35A3. One of the things I noticed about the truck was that the tires on the driver's side of the truck are all flat, but the ones on the passenger side are all holding air. Also, the CTIS ECU will not turn on.

    Based on a CTIS pipe diagram I saw on FP-5 of TM9-2320-386-24-1-2, each of the axles has an air branch coming off the power manifold. I don't know much about this manifold, but based on reading on this website, it sounds like it doesn't control individual branches. Am I wrong with that understanding? If I'm not wrong, is it totally possible that each of the tires and/or rims on the driver's side has some kind of defect?

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    Super Moderator gringeltaube's Avatar
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    Even if no visible defects, if that truck has been sitting like that for more than a few days, those flat tires may be ruined anyway and should not be reused on the road.

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    4 Star General cattlerepairman's Avatar
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    What Gringeltaube said. There have been enough reports of the M35A3 tires blowing after re-inflation, often while driving, to consider this a serious issue if the truck has been sitting on one or more deflated tires for a long time. I would have zero confidence in these tires, other than for loading the truck onto a trailer. M35A3 owners will chime in as to whether it is worth fixing the CTIS or removing it. The CTIS related hub and axle parts for the A3 are pricey.
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    Sergeant HDN's Avatar
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    If I bought the truck, I'd try to fix the CTIS just because I'd like to keep original equipment functional if I can. I'm just not sure what would cause all the tires on one side to be flat, but I don't really have an understanding of how the manifold divides the air among the wheels. I thought it was per axle and not per side. Thoughts?

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    4 Star General frank8003's Avatar
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    Print out those FP5 diagrams and study some more and you will find the answers you seek.
    Look at the exhaust as to do with the power manifold. Disconnect at the wheels on drivers side, put new tires and work on it. It works 50%.
    I was here, had a good time.

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    I'm in exactly the same boat with regards to flat tires - they're holding air enough to get it on the trailer. But there is zero chance I'll be trusting those on the road, ever. And of course, I too need to work through the leaks in the system. Don't even know if the CTIS computer turns on (no batteries in truck presently), but those aren't that expensive. I'm just hoping the hardware on the axles/wheels is ok and doesn't all need replacing...

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    4 Star General glcaines's Avatar
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    The CTIS manifold on M35A3 trucks does not control individual wheel valves. They are controlled as a group. The manifold is basically one storage tank. I would suspect that someone has replaced the grommets and o-rings on one side of the truck but not on the other side. A3 tires will hold air fine with the CTIS installed if the o-rings, and especially the grommets under the tubes for the schrader air valves are replaced, installed properly and correctly torqued to 45 - 60 Ft Lb. You can use soapy water to determine if any of the CTIS wheel valves and/or tubing is leaking, but this can be done after the O-rings and grommets are sorted out. The wheel valves themselves are also very simple and easy to take apart and clean if needed. The CTIS is actually a very simple set-up and easy to work on. The failures result from poor maintenance. Most of these trucks have been sitting for decades with minimal use or maintenance. The only really expensive components are the wheel bearings on the rear where the seal is combined with the wheel bearing and supplied as one component.
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    Sergeant HDN's Avatar
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    Thank you for your feedback and ruling out the manifold for this issue! I think I'll see if I can bargain the truck around a new set of tires.

    I read somewhere that the thicker commercial truck o rings are the way to go with the rim. Are there commercial alternatives to the other CTIS seals on the rim?
    Last edited by HDN; 09-20-2019 at 16:30.

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